This invention relates to heat exchangers, and in particular, to oil coolers of the so called xe2x80x9cdoughnutxe2x80x9d type that can be used separately or in conjunction with oil filters in automotive and other engine and transmission cooling applications.
Oil coolers have been made in the past out of a plurality of stacked plate pairs located in a housing or canister. The canister usually has inlet and outlet fittings for the flow of engine coolant into and out of the canister circulating around the plate pairs. The plate pairs themselves have inlet and outlet openings and these openings are usually aligned to form manifolds, so that the oil passes through all of the plate pairs simultaneously. These manifolds communicate with oil supply and return lines located externally of the canister. An example of such an oil cooler is shown in Japanese Utility Model Laid Open Publication No. 63-23579 published Feb. 16, 1988.
Where the oil cooler is used in conjunction with an oil filter, the plate pairs are usually in the form of an annulus and a conduit passes through the centre of the annulus delivering oil to or from the filter located above or below the oil cooler and connected to the conduit. The oil can pass through the filter and then the oil cooler, or vice-versa. Examples of such oil coolers are shown in U.S. Pat. No. 4,967,835 issued to Thomas E. Lefeber and U.S. Pat. No. 5,406,910 issued to Charles M. Wallin.
A difficulty with these prior art oil coolers, however, is that they are not particularly efficient. They also often suffer from the disadvantage of high pressure drop on the oil side of the cooler.
The heat exchanger of the present invention is very efficient with relatively low pressure drop. A first exchange fluid travels circumferentially through ringlike plate pairs, and all of a second heat exchange fluid flows between the plate pairs transversely relative to the first heat exchange fluid.
According to one aspect of the invention, there is provided a heat exchanger which comprises a plurality of stacked plate pairs consisting of face-to-face, mating ringlike plates. Each plate has an outer peripheral flange, an annular inner boss having a portion thereof located in a common plane with the peripheral flange, and an intermediate area located between the peripheral flange and the inner boss. The peripheral flanges and inner bosses in the mating plates are joined together. The intermediate areas have spaced-apart portions to form an inner flow passage between the plates. The plate intermediate areas have spaced-apart intermediate bosses located between the outer peripheral flange and the inner boss that extend from the intermediate area in a direction opposite to the peripheral flange and inner boss. The intermediate bosses define inlet and outlet openings and are arranged such that in back-to-back plate pairs, the intermediate bosses are joined and the respective inlet and outlet openings communicate to define inlet and outlet manifolds for the flow of a first exchange fluid circumferentially through the inner flow passages from the inlet manifold to the outlet manifold. The adjacent intermediate areas in back-to-back plate pairs define outer flow passages therebetween. The outer flow passages extend substially between the inner bosses and the outer peripheral flanges of the respective back-to-back plate pairs. Also, a header encloses one of the inner bosses and outer peripheral flanges. The header includes a flow port for the flow of a second heat exchange fluid therethrough to force the second heat exchange fluid to flow transversely through the outer flow passages between the inner bosses and the outer peripheral flanges.
According to another aspect of the invention, there is provided a method of transferring heat energy between lubricating fluids and engine coolant. The method comprises the steps of providing a plurality of ringlike, closely spaced-apart, stacked plate pairs having inner flow passages therebetween and outer flow passages between the plate pairs. Each plate has an outer peripheral flange, an annual inner boss having a portion there of located in the common plane with the peripheral flange, and an intermediate area located between the peripheral flange and the inner boss. The outer flow passages extend substantially between the inner bosses and the outer peripheral flanges of respective adjacent back-to-back plate pairs. All of one of the fluid and the coolant is passed circumferentially through the plate pairs, and all of the other of the fluid and the coolant is passed transversely between the plate pairs.